Value of Foreign Currency Exchange(In INR/Per Transaction) GST Rate applicable Under rule 32(2)b of CGST & SGST Rule 2017: Service Tax: Upto Rs. 1,00,000: 1% of the Gross amount subject to minimum Rs. 250/-0.14% of the amount of currency, subject to minimum of Rs. 35/-From Rs. 1,00,001 to 10,00,000 GST on Foreign Exchange Conversion is levied at 18%. GST on the supply in the above example will be 100 * 18% = 18 Rs. Now, in another situation, if Mr. Raghav wants to purchase 100 USD at the rate of 1 USD = 70 INR, and the RBI Reference Rate is INR 72 per USD, then. The value of supply will be: (72-70)*100 = 200 INR. And the GST charged will be: 200 * 18% = 36 Rs. Recommended: GST on Commission and Brokerage. Sub-case 2: RBI Reference Rate is not given Sales in Foreign Currency. For such sales with GST, you must convert the following items in the tax invoice into Singapore dollars using an approved exchange rates for GST purpose (185KB): Total amount payable excluding GST; Total GST payable; and. Total amount payable including GST.